Field of the Invention
The present invention relates to a device for connecting two pieces of equipment together. By way of example, one of the pieces of equipment is a computer unit and the other is an input peripheral such as a keyboard, a pointer device of the mouse or touchpad type, or a mass data storage peripheral such as an external hard disk or a solid state memory. The invention also provides a docking station for such a piece of equipment.
Brief Discussion of the Related Art
Computer systems are generally built around a computer unit, commonly referred to as a central unit, with peripherals that are connected thereto. The computer unit incorporates one or more processors, and memories storing an operating system and applications that are executed by the processor(s). The peripherals are connected to the computer unit by parallel or serial links. Serial links that make use more particularly of a universal serial bus (USB) type protocol have become widespread in computer systems, both for consumers and in industry. That type of link is also suitable for use in connecting peripherals to one another.
Nevertheless, that type of serial link presents a certain number of drawbacks that make such links difficult to use in certain highly constrained applications, in particular concerning electrostatic discharge.
Amongst those drawbacks, there is the absence of electrical isolation that can be extremely harmful for the elements that are connected together thereby when lightning strikes the electrical insulation to which one of the elements is connected.
This risk is all the greater in modern aircraft where the fuselage is less and less capable of acting as a Faraday cage because of the increasing use of composite materials to make fuselages, where such materials are poor conductors. This makes it necessary to have recourse to non-linear components of the spark gap, lightning diode, or varistor type. The electrical levels that need to be withstood are relatively great (1500 volts (V) and 500 amps (A) for a period of 100 microseconds (μs)), so such components are designed to be highly stressed. By way of example, a component capable of limiting a signal to 54 V must be capable of absorbing 40 kilowatts (kW) for 100 μs with a temperature de-rating of 60%. As a result, such components are very bulky and give rise to large amounts of stray capacitance, leading to problems of rapid signal attenuation. Furthermore, the circuits that make use of such components can be tested only by using tooling that is expensive and not without danger both for the components of the circuit and for the operators of such tooling.
In addition, the low conductivity of composite materials prevents the use of a hardware ground as a reference in terms of electromagnetic compatibility, at least for low frequency components. The maximum coupling capacitance to hardware ground is also limited to 150 nanofarads (nF), or even much less, since it may be less than 100 picofarads (pF).
Furthermore, that type of link presents other drawbacks when used in computer systems on board aircraft:                linking is possible over a short distance only even though computer systems may be split up on board aircraft in order to optimize utilization of the space available, such that the various elements of an on-board computer system are often remote from one another; and        a lack of feedback based on experience concerning links of this type in aviation applications.        
As a result, in such applications, the power supply and communications functions are kept separate.
All or some of the above-mentioned drawbacks are also present with various links of other types and in particular of the following types: PS2, ARINC 429, CAN bus, . . . , regardless of the intended application.